[CT-84] Benchmark suite from CT-65 isn't run in CI — no performance regression gate

[mftee]

Overview

CT-65 added benchmarks establishing performance baselines under contract/benches/, but nothing indicates they run as part of CI — without that, a future change can silently regress verification/hashing performance with no automated signal.

Tasks

• Add a CI job (can be non-blocking/informational initially) that runs cargo bench and reports results
• Optionally compare against the committed baseline and flag significant regressions

Acceptance Criteria

• Benchmarks run automatically in CI on a defined schedule or on relevant PRs, with results surfaced somewhere visible

Notes for Contributors

Comment below to be assigned.

[Kenisank]

Hi maintainer, I would like to solve this issue